Ya know when I first started working on cars in the early 70's, I remember thinking why plug the vacuum line to the distributor. I didn't know ***** from shineola. At some point in time I realized I needed to plug the line coming from the vacuum source. So between the first tinkering and when I found out the correct way, I would set timing with the light, then drive a ways, leave the engine running and turn the distributor . I did this numerous times until the car (1962 Chevy impala with a 327 and a power glide tranny) ran the best.
I didn't have a clue at that point in time what manifold vacuum was, or what it did. To my credit, I was just a young lad of 17. I did know how to stab a distributor and find TDC. My dad knew less than I did, had it not been for High School shop classes I'd have been totally lost.
Remember this was before Calculators when math equations were done on a slide rule. Didn't have a clue about that either, it did make a great straight edge though.

Sorry about being so long winded, I like to make a short story long, and I must be in a Reminiscing mood tonight.

Edit, still have the slide rule, and still don't have a clue.
Bill
Moral of the story, make sure the vacuum line is plugged coming from the carb.

Their is a oil wick in the center of the distributor shaft when you remove the rotor. It's to get a few drops of oil at oil change. It is to keep the fly-weights from sticking.

If your carb was lean to the point of detonation and melting pistons the throttle would feel spongy. And the motor would be lazy to respond. Unless a manifold leak is only effecting 1 cylinder. Holley's like backfiring out the carb when things lean out to that extreme in my experience.

2Xtreme. For what it's worth I just had a very similar problem. Well after I recurved my dizzy (changed one of the springs to the lightest in the kit)and fixed my exhaust leak I was having pinging under load in every gear. Now I figured my total advance was coming in too early so I changed the other spring that came in the dizzy to the medium spring from the kit. This fixed my ping and moved my curve up the rpm alittle. Please note this was all done with a CRT dizzy and not stock though. With that said when your checking things out it might help to start out with plotting your curve so you have something to work off of. It could be one of the springs in you dizzy has gotten weak or broke. Hope you figure it out.

There is no app for AL 5503's w/Jeep. Where did you get that app.http://www.autolitecatalog.com/PartD...px?b=A&pn=5503
NEVER/EVER use LPG to hunt for vac. leaks for god-shakes.
Soapy water is much better for this and you can see where the bubbles go.....AND IT WON'T EXPLODE if you have an arc off your SP wires etc. that you don't know about.......
You want the 195* t'stat.

FWIW... and I'm not trying to stir the pot, so don't take it that way, propane is a great way to find a vacuum leak. It's quick, easy, and it doesn't make a mess. It sucks right in through the leak and smooths the engine out instantly. It won't explode, and the exhaust manifold doesn't get hot enough to ignite the tip, so there is no flame either. The old methods of carb cleaner, etc, are tried and true, and there's nothing wrong using them. It's just preference.

Lumpy... your idea of soapy water is also a good method for finding leaks, but not vacuum leaks. There won't be any bubbles.

__________________KerrdogGo Fish!<*////><

But the right word at the right time... "Hey, give me a little hug!" That's the difference between lightning and a harmless lightning bug!

There is no app for AL 5503's w/Jeep. Where did you get that app.http://www.autolitecatalog.com/PartD...px?b=A&pn=5503
NEVER/EVER use LPG to hunt for vac. leaks for god-shakes.
Soapy water is much better for this and you can see where the bubbles go.....AND IT WON'T EXPLODE if you have an arc off your SP wires etc. that you don't know about.......
You want the 195* t'stat.

LG

The 5503's (or equivelent) was recommended by Shawn in a post above:

Quote:

Originally Posted by swatson454

...Since new plugs are on the menu, you might want to drop down a couple of heat ranges and do something like an Autolite 5503 or equivalent....Shawn

There are many, many credible recommendations on the internet regarding using propane to find vac leaks.

BUT, if it is going to a point to booger up this thread, I will use another method. Probably the carb cleaner thing, because I honestly don't have much faith in the soap bubbles.

FWIW... and I'm not trying to stir the pot, so don't take it that way, propane is a great way to find a vacuum leak. It's quick, easy, and it doesn't make a mess. It sucks right in through the leak and smooths the engine out instantly. It won't explode, and the exhaust manifold doesn't get hot enough to ignite the tip, so there is no flame either. The old methods of carb cleaner, etc, are tried and true, and there's nothing wrong using them. It's just preference.

Lumpy... your idea of soapy water is also a good method for finding leaks, but not vacuum leaks. There won't be any bubbles.

he is saying if the bubbles "dissappear" there is a leak. not sure if it will work on a hot manifold but it is a non volatile way of finding a leak.